Updated at 12 p.m. ET
SAN ANTONIO - A Texas bomb squad searched a county courthouse that serves San Antonio and moved up the routine check of a nearby convention center -- the venue for an intelligence conference -- after police arrested five foreign nationals Wednesday.
Investigators found 90-day visas, maps, cell phones and computers inside a rented RV parked outside the courthouse, authorities said.
The men, all in their 20s, were unarmed when they were arrested about 1:30 a.m. at the old Bexar County Courthouse, said sheriff's department spokesman Louis Antu. Three of the men were caught inside. The others were outside near the RV, which had California plates but may have been rented in New York, Antu said.
Antu said he had no information to indicate the break-in was related to terrorism and that the incident was being investigated as a burglary.
"They can't explain adequately why they're in one of our historical buildings at 1:22 in the morning," San Antonio police Capt. Cris Anderson told CBS Radio News.
The men have told police they are French Moroccan and Muslim, Anderson said. Antu said FBI and federal immigration agents were called in because the men aren't from the U.S. and authorities are working to determine their nationalities.
"We're in the process of finding out what was going on or why they were in the building," Antu said. "We got ICE and the FBI involved because we're dotting I's and crossing T's to make sure we don't have anything more serious."
Antu said all five men remained in custody as of midmorning and were being interviewed.
"We don't know exactly who they are," Antu said. "Just because they have their visas ... who are they really?"
Authorities said the men may have entered the historic building, which remains in use as a county court, through a window or rooftop door. The courthouse is connected by a tunnel to a justice center that has additional county and state district courtrooms.
The San Antonio Express-News reports that, according to an official, some of the men appeared intoxicated while talking with investigators.
Officers who arrived first at the courthouse had called in bomb-sniffing dogs as a precaution early Wednesday, said Bexar County spokeswoman Laura Jesse. A full security sweep was conducted before the courthouse opened at 7 a.m., she said.
The downtown break-in happened blocks away from dozens of U.S. intelligence officials who are in town for an annual convention. Michael Vickers, the undersecretary of defense for intelligence, was scheduled to speak at the conference Wednesday along with Air Force Gen. Robert Kehler, chief of U.S. Strategic Command.
The intelligence conference, called the GEOINT Symposium, started Sunday and bills itself as the "nation's largest intelligence event of the year." Anderson said that "daily sweeps" have been conducted at the Henry B. Gonzalez Convention Center because of the conference.